The method for manipulating speed changing in a speed changing arrangement of an ordinary bicycle is to utilize a chain to skip up or down between the pedal gear of the pedal shaft of the bicycle body and the chain sprocket set of the rear wheel so as to select and replace the chain sprockets among different diameters to achieve the effect of speed changing. It is well known to those skilled in the prior art that this type of speed changing potentially bears several inevitable disadvantages:
1. Although there are a lot of bicycle products in the market with the speed changing capability of ten speed stages or more, however, after interviewing with many experienced riders, it is found that, in spite of the various speed stages, the distinction between adjacent speed stages is not significant; in the view of practicality, even the car or motorcycle has no more than five speed stages in speed changing, it is therefore not necessary to have so many speed stages, but should rather enhance the difference between speed stages so as to decrease the number thereof; the reason for applying so many speed stages is due to the characteristics of the speed changing methods which utilize the chain to skip across gears wherein if there were only several practical chain sprocket sets chosen, it will be difficult for the chain to skip across gears and the uncertain phenomenon in speed changing may occurs, since the difference between the diameters of the chain sprockets is too large.
2. It is very difficult for the rider in riding to clearly know what speed stage the gear is really in now, because it is hard to recognize the speed stage even from the appearance or from the feeling.
3. It may readily cause the serious friction and chain coming-off phenomenon while the chain is skipping across between the chain sprocket sets. In the case, for example, of speed changing from the lowest speed to the highest speed, the chain at least has to skip three chain sprockets therebetween, thus such a condition may readily provoke the gravity wearing phenomenon for the chain on the surfaces of the gears.
4. The noise phenomenon occurs frequently during riding. This is because the adjacent chain sprockets are too close, so that, after the chain has been pushed for gear shifting, although the gear shifting has been completed, the chain may still contact the side surface of the adjacent sprocket gear due to the slight deviation, which may generate noise via the friction therebetween and may uncomfortably annoy the rider.
It can be found from the associated situations mentioned above and the live observation that, unless in the real case of hill climbing or high speed riding, the existent speed changing function of an ordinary bicycle is usually in fact spared and unused. In order to make the practical features for the speed changing function of the bicycle more publicized, the present inventor has diligently studied this object, and has finally innovated the present novel speed changing arrangement; that is, the present invention is related to a method of speed changing wherein by means of the arrangement of a gear shifting shaft set in the spacing directly between the speed changing gear set and the output gear set, the gear shifting process can be first manipulated to the neutral gear state and then change to the desired gear, which may improve and replace the conventional methods of speed changing utilizing a chain to skip across gears. It can be found from measurements and evaluations of the real application conditions that the speed changing needed in riding an ordinary bicycle may generally require only four speed stages of speed changing to satisfy the demands of an ordinary rider: the starting stage (hill climbing), the normal low speed stage (against the wind and loaded), the normal high speed stage (along the wind), and the high speed stage. Therefore the present invention employs the four speed stages of speed changing as the design base. After practically realizing a prototype bicycle, and repeatedly testing and improving said bicycle in the fields, it has been proved that the original expected goals of the design have been achieved actually (the design principles of the present invention can be essentially expanded to five or six speed stages according to the need).